Biology Concept 28.2: Protists and Mitochondria

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Questions and Answers

What is unique about the oomycetes?

They are single-celled organisms.

They have plastids and perform photosynthesis.

They have cell walls made of cellulose.

They acquire nutrients through parasitism or decomposition. (correct)

What is the function of the alveoli in alveolates?

To store nutrients

To regulate the cell's water balance

To provide mechanical support

Unknown function (correct)

What are the three clades included in the alveolates?

Dinoflagellates, apicomplexans, and fungi

Apicomplexans, ciliates, and bacteria

Oomycetes, fungi, and dinoflagellates

Dinoflagellates, apicomplexans, and ciliates (correct)

What causes the water to appear brownish red or pink during a red tide?

The presence of carotenoids Signup and view all the answers

What is the effect of red tides on invertebrates and fishes?

They cause massive kills Signup and view all the answers

What is facilitating more frequent red tides?

Ocean warming caused by climate change Signup and view all the answers

What is the characteristic feature of dinoflagellates?

They have two flagella housed in the grooves of armor-like cellulose plates Signup and view all the answers

What is Phytophthora infestans?

A parasite that causes potato late blight Signup and view all the answers

What is the current status of the root of the eukaryotic tree?

It is still unknown and a subject of ongoing research Signup and view all the answers

What is a characteristic feature of the excavates?

Presence of modified mitochondria Signup and view all the answers

What is the primary source of energy for diplomonads?

Anaerobic metabolism Signup and view all the answers

What is the by-product of anaerobic metabolism in parabasalids?

Hydrogen gas Signup and view all the answers

What is the primary habitat of most diplomonads and parabasalids?

Anaerobic environments Signup and view all the answers

What is the function of the 'excavated' feeding groove in some excavates?

Capture prey Signup and view all the answers

Which group of excavates includes the parasite Trichomonas vaginalis?

Parabasalids Signup and view all the answers

What is the estimated number of people infected with Trichomonas vaginalis per year?

140 million Signup and view all the answers

What does the acronym SAR stand for?

Stramenopiles, Alveolates, and Rhizarians Signup and view all the answers

What is a characteristic feature of stramenopiles?

They have a 'hairy' flagellum paired with a 'smooth' flagellum. Signup and view all the answers

What is the primary component of a diatom's cell wall?

Silicon dioxide Signup and view all the answers

What is the estimated number of diatom species?

100,000 Signup and view all the answers

Why are diatoms important in the ocean?

They are the primary producers of the ocean. Signup and view all the answers

What happens to dead diatoms in the ocean?

They sink to the ocean floor, where decomposition is slow. Signup and view all the answers

What is the proposed use of diatom blooms in reducing atmospheric CO2 levels?

To fertilize the ocean with essential nutrients Signup and view all the answers

Which group of stramenopiles includes brown algae?

All of the above Signup and view all the answers

What is the characteristic that gives green algae their name?

Their green chloroplasts Signup and view all the answers

Which group of green algae includes the algae most closely related to plants?

Charophytes Signup and view all the answers

What is the most common environment for chlorophytes?

Fresh water Signup and view all the answers

What is a key role that protists play in their habitats?

Symbiont Signup and view all the answers

Which of the following protists is a symbiont that benefits its host?

Dinoflagellates Signup and view all the answers

How do some green algae, such as Caulerpa, achieve larger size and greater complexity?

Through repeated division of nuclei with no cytoplasmic division Signup and view all the answers

What is a characteristic of nearly all chlorophyte species?

They have biflagellated gametes with cup-shaped chloroplasts Signup and view all the answers

What is the primary source of energy for photosynthetic protists?

Light Signup and view all the answers

What is the effect of adding nutrients to photosynthetic protists?

Population explosion Signup and view all the answers

Which process has evolved in some chlorophytes, including Ulva?

Alternation of generations Signup and view all the answers

What is the name of the group that includes protists that are closely related to fungi and animals?

Unikonts Signup and view all the answers

What is the consequence of a population boom of photosynthetic protists?

Formation of marine 'dead zones' Signup and view all the answers

What is the characteristic of the life cycle of Chlamydomonas, a unicellular chlorophyte?

It has a complex life cycle with both sexual and asexual reproductive stages Signup and view all the answers

What is the effect of increasing sea surface temperature on photosynthetic protists?

Decrease in growth and biomass Signup and view all the answers

What is necessary for phytoplankton communities to thrive?

Upwelling of cold, nutrient-rich water Signup and view all the answers

What is the effect of warm surface water on phytoplankton communities?

Barrier to upwelling Signup and view all the answers

Study Notes

Eukaryotic Tree and Protists

The root of the eukaryotic tree is unknown, and new groups of protists have been discovered, but their relationships to supergroups are unresolved.
Examples of unresolved groups include haptophytes, cryptophytes, and hemimastigophores.

Excavates

Excavates are characterized by their cytoskeleton and some have an "excavated" feeding groove on one side of the body.
The excavates include three monophyletic groups: diplomonads, parabasalids, and euglenozoans.
Diplomonads and parabasalids lack plastids and have reduced mitochondria, and most live in anaerobic environments.
Diplomonads have two equal-sized nuclei and multiple flagella, and many are parasites, such as Giardia intestinalis.
Parabasalids have reduced mitochondria, called hydrogenosomes, that generate some energy anaerobically, and release hydrogen gas as a by-product.

SAR Supergroup

SAR is a monophyletic supergroup named for the first letters of its three major clades: stramenopiles, alveolates, and rhizarians.
Stramenopiles include some of the most important photosynthetic organisms on Earth, and most have a "hairy" flagellum paired with a "smooth" flagellum.

Stramenopiles

Diatoms are unicellular algae with a unique two-part, glass-like wall of silicon dioxide, and are an important group of stramenopiles.
Diatoms are so abundant and widespread that their photosynthetic activity affects global CO2 levels, and promoting diatom blooms by fertilizing the ocean with essential nutrients is a proposed approach to reduce atmospheric CO2 levels.
Oomycetes are related to plastid-bearing groups, but do not have plastids or perform photosynthesis, and acquire nutrients through parasitism or decomposition.
Brown algae are another important group of stramenopiles.

Alveolates

Alveolates have membrane-enclosed sacs (alveoli) just under the plasma membrane, and three clades included in the alveolates are the dinoflagellates, the apicomplexans, and the ciliates.
Dinoflagellates are abundant components of marine and freshwater phytoplankton, and have two flagella housed in the grooves of armor-like cellulose plates that surround the cell.
Dinoflagellate blooms cause "red tides" where the water appears brownish red or pink due to the carotenoids present in their plastids, and are toxic and can cause massive kills of invertebrates and fishes.

Green Algae

Green algae are named for their green chloroplasts, which are structurally and chemically similar to those found in plants, and form a paraphyletic group that includes the charophytes and the chlorophytes.
Charophytes include the algae most closely related to plants, and most chlorophytes live in fresh water, although there are many marine and some terrestrial species.
Larger size and greater complexity evolved in green algae by three different mechanisms: formation of colonies, formation of true multicellular bodies, and repeated division of nuclei.

Unikonts

Unikonts are a supergroup that includes protists that are closely related to fungi and animals.

Protists in Ecological Communities

Protists are found in diverse aquatic and moist terrestrial environments, and play two key roles in their habitats: that of symbiont and that of producer.
Some protist symbionts benefit their hosts, while others are parasites.
Photosynthetic protists are producers, and are limited by nutrients, and populations explode when nutrients are added, leading to major ecological consequences.
Phytoplankton communities rely on upwelling of cold, nutrient-rich water from the below, and warm surface water acts as a barrier to upwelling.

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Description

This quiz covers the concept of excavates, including protists with modified mitochondria and unique flagella, as well as unresolved groups like haptophytes and cryptophytes. Learn about the characteristics of these protists and their relationships to supergroups.